This disclosure generally relates to the use of iron salts to lower ammonia emissions and sequester soluble phosphorous in animal litter or bedding materials, and more particularly, to the use of a ferric sulfate composition applied as a granular solid to the animal litter.
Ammonia is a common by-product of animal waste due to the often inefficient conversion of feed nitrogen into animal product. Livestock and poultry are often fed high-protein feed, which contains surplus nitrogen, to ensure that the animals' nutritional requirements are met. Nitrogen that is not metabolized into animal protein (i.e., milk, meat, or eggs) is excreted in the urine and feces of livestock where further microbial action releases ammonia into the air during manure decomposition. Because of this, in-house air quality is a major concern. Producers spend much of their time and investment in maintaining good air quality to maximize growth and performance of livestock. Ammonia levels of 25 ppm or more can lead to significant health problems for the animals including respiratory infections and eye lesions, or even death of the animal. For example, previous work has correlated negative bird performance with poor indoor air quality in poultry growing and holding areas due to ammonia (NH3) and dusts. Low growth rates, low feed utilization rates, high mortality rates, costs of house ventilation especially in the cooler months are all losses that can be related to the quantities of ammonia and ammonia compounds generated by livestock. As used herein, the term “livestock” is intended to refer to poultry, swine, cattle, horses, and like animals that are generally contained within a confined area for extended periods of time.
Ammonia is a colorless, alkaline, water-soluble gas that is produced by microbiological deamination or reduction of nitrogenous substances. Animal litter, a combination of fecal material, spilled feed, bedding material, and the like, provides a source of ammonia emissions within floor-reared production facilities. For example, birds excrete excess nitrogen (N) in the form of uric acid and it is the microbial decomposition of uric acid within the litter, which is the primary source of ammonia generation. Litter type, management, humidity, pH, and temperature all affect ammonia generation and concentration. Ammonia volatilization is a complex physical and chemical process and emissions are generally related to four factors: ammonium ion concentration of the medium, temperature of the medium, pH of the medium and turbulent transport of the ammonia from the medium. There is a trend within the industry for tighter house design and less frequent litter or bedding material removal. These two factors have the potential to dramatically increase the ammonia concentration within production facilities.
With respect to poultry houses, commercial poultry producers generally employ some form of ventilation to mitigate volatile ammonia concentrations emanating from decomposing animal litter in their houses. Current ventilation methods consume energy both for air exchange and for heating makeup air.
Animals are also susceptible to ingestion of materials used in litter and/or bedding material treatments. A typical material used is alum, i.e., aluminum sulfate. Application of urease inhibitors to cattle and/or swine manure has effectively limited urea hydrolysis in laboratory and field studies. Such inhibitors are easily degradable and must be continuously applied to manure in order to reduce the production of ammonia from urea. Still other litter amendment materials include ferrous sulfate, liquid ferric sulfate or chloride, and the like. In U.S. Patent Application No. 2006/0005784 A1, the use of the liquid ferric sulfate or chloride is described as an advantage over granular reagent grade ferric sulfate crystals because the animals can ingest the granular form of ferric sulfate crystals and the use of the solid form to be distributed in practical quantities is reported to be marginally effective. The ferric sulfate crystals, whether they be technical or reagent grade, have a yellowish to white color that is generally distinguishable from the litter and common materials used in the house such that it can be visible to the animals, which leads to accidental ingestion since the animals can confuse the litter amendment with feed.
In addition to the production and welfare impacts, there is growing public concern over outdoor air quality and the amount of pollutants released by animal feeding operations (AFOs). Of greatest interest are the emissions of ammonia and particulate matter. Environmental air and water quality potentially can be impacted by animal production emissions in the form of atmospheric nitrogen deposition. Since these emissions originate from within the production facilities, strategies to reduce the generation of dust, ammonia, and odors within houses will have a corresponding impact on the level of house emissions.
One technique to reduce emissions from production facilities, such as poultry production barns, lowers the pH of the litter to maximize conversion of volatile ammonia to ammonium ion (NH4+). Application of litter treatments to reduce the pH of the litter is the mechanism used to accomplish the pH reduction. Typical acidifier litter treatments such as alum are effective for short-term ammonia reduction, up to approximately two weeks. Amounts required for longer-term effectiveness in chemically binding litter nitrogen are corrosive, represent additional hazards to the animals, and are difficult to apply with the animals present in the production facility.
Soluble litter phosphorous (P) in the form of phosphates (PO4−2) is another concern when land-applied to lands already overburdened with phosphates and susceptible to surface water runoff and edge of field erosion. Products that can bind soluble phosphorous in land-applied animal litter and/or bedding material would benefit the industry in addressing water quality impacts from these various operations.
In view of the foregoing, there accordingly remains a continued need in the industry to more efficiently address the problems associated with volatile ammonia emissions and soluble phosphorous in animal litter and/or bedding materials.